1. Field of the Invention
The present invention relates to an active-matrix-type display device, and more particularly to a drive-circuit-integral type display device which forms a drive circuit on the same substrate as a display region.
2. Description of the Related Art
A TFT (Thin Film Transistor) type liquid crystal display device which includes a switching element in a pixel portion has been popularly used as a display device of a personal computer or the like. Further, the TFT-type display device is also used as a display device of a personal computer or the like. The display device used in the portable device is required to be further miniaturized and to exhibit the further reduction of power consumption compared to a conventional liquid crystal display device.
As the display device which possesses the structure effective for the miniaturization, there has been known a so-called drive-circuit integral type display device which also forms a drive circuit which supplies signals to a pixel portion.
In incorporating the circuit in the display device, there arises a drawback that a voltage level of an inner circuit and a voltage level of an input signal from an external device differ from each other. To overcome this drawback, a level shift circuit which converts a voltage level is used.
JP-A-2003-302946 describes a level shift circuit which is used in a drive-circuit integral type display device.